It is desired to withdraw liquid from a sealed container. Such a situation arises in agriculture when it is desired to connect a sealed container to a spraying device and to spray liquid agrochemical from the container onto crops. Normal unsealed arrangements where the container is open to atmosphere allow the possibility of leakage, even via air bleed arrangements, as the liquid slops around in the container in use. There are environmental, health and/or economic reasons for preventing the possibility of leakage.
One proposal enabling the container to be completely closed and yet enabling liquid to be withdrawn is a collapsible container, usually inside a rigid box. There are problems with this, however. For example it is not possible to completely empty the container. The user always pays for more than can be extracted from the container.
In accordance with the invention there is provided, a cap for a liquid container, the cap incorporating an outlet and an air bleed valve, the air bleed valve comprising: a housing opening through the cap, in use, to the outside of the container; a non return valve in the housing to prevent fluid leaving the container via the housing; and a breather tube having one end connected to the interior of the housing downstream of the non return valve, so that when the container is inverted in use, a free end of the breather tube is above the level of the liquid in the container, enabling liquid to be withdrawn from the outlet e.g. by gravity.
In use, the bleeder tube and housing connect the down stream end of the non return valve to air above the liquid level in the container. If the liquid were allowed direct communication with the non return valve, the hydrostatic pressure head would be sufficiently high as to prevent the non return valve opening to allow air to enter the container when liquid is withdrawn, which would prevent the withdrawal of any liquid by gravity.
Preferably, the non return valve comprises a resilient tube, open at one end and closed to a slit at the other end, so that air can flow through the valve from the open end to the slit end but not in the reverse direction.
The cap may be fitted to the feed pipe of an agricultural sprayer, e.g. a hand held back pack sprayer. A container of agrochemical is connected to the sprayer by removing the container's cap and fitting the sprayer's cap. The container is then inverted. Any small amount of the liquid which gets into the bleeder tube is prevented from leaking out by the non return valve.
The invention also extends to a container for liquid, the container incorporating an outlet and an air bleed valve, the air bleed valve comprising: a housing opening through to the outside of the container; a non return valve in the housing to prevent fluid leaving the container via the housing; and a breather tube having one end connected to the interior of the housing downstream of the non return valve, so that when the container is inverted in use, a free end of the breather tube is above the level of the liquid in the container, enabling liquid to be withdrawn from the outlet by gravity.